Originally Posted by
Frodo
Dany thought her dragons couldn't be stopped by the fleet, which was true for Drogon when he decimated the fleet outside Kings landing. Rhaeger obviously wasn't as quick as Drogon, same with Viserion up north.
They only ran into the night after Melisandre gave them swords of fire. Remember, the Dothraki aren't exactly strategists. They won wars by sheer force and weren't easy to control, even for Danys. There was a lot of unsullied, but I do think they exaggerated how many died at Kings Landing. But that's TV land for you.
If Cersie kills Dany at the gates during parlay she would lose a lot of backers and would still have to deal with the Unsullied army, the Dothraki, plus other houses would join the Men of the North and defeat her anyway. If she beats Danys in battle, all houses would have to bend the knee to her. Cersei is evil, but not stupid.
Jon and Tyrion spent time with the Dothraki / Unsullied, it's not ridiculous to imagine that they could learn their language. But that's not really a big plot hole, how many movies do the German soldiers speak English and what-not? You've got to allow characters to understand each other.
The dragons struggling in the snow isn't that hard to believe. The night king was born of dragon glass and could only be killed with dragon glass or Valerian steel, I'm pretty sure that was explained in the show (it may have been in the book only) Don't forget, Danys can't be hurt by fire either. So thats not hard to believe. The not beating the ship's one day and beating them the next is classic tv trope. All it needed was a training montage.
Remember, it's a tv show. Some things are allowed to be skipped over to make it easier to tell the story.